Patent GB-770282-A (GB)
Title: Fuel injection apparatus for reciprocating internal combustion engines
Inventor: CATFORD ADRIAN LESLIE
IPC: F02D1/02
Filed: 1954-11-19
Abstract: 770,282. Fluid-pressure. servomotor-control systems. NAPIER & SON, Ltd., D. Nov. 19, 1954 [Dec. 1, 1953], No. 33315/53. Class 135. In a fuel system for reciprocating internal - combustion engines in which fuel under pressure is supplied to the pump supply chamber of a reciprocating fuel injection pump through one orifice and excess fuel is continuously withdrawn from the pump supply chamber through another orifice so that the volumetric rates of flow through the two orifices determine the net fuel flow to the pump, means are provided for maintaining a constant selected rate of fuel flow through one of the orifices, and means responsive to the pressure drop across the other orifice control mechanism for varying the rate at which fuel is delivered by the pump to the engine. In Fig. 1, a constant flow is maintained through an orifice 50a in the return line 45, 47 from the fuel injection pumps 1, 2. An enginedriven pump 3a fitted with a relief valve 48 and a by-pass valve 49 supplies liquid fuel from a tank 40 through a metering device 43 to the fuel injection pumps 1, 2. Excess fuel is returned to the tank 40 through the pipes 45, 47 and a constant-flow unit 46. The metering unit 43 has a metering orifice comprising the variable area between a ported sleeve 60 adjusted by a cam 62 on a shaft 63 operated by a power control lever 8a and a conical valve member 65 adjustable by a cam 68. The pressure drop across this metering orifice is applied to a diaphragm 70 which actuates a balanced servo-control valve 17a. The valve 17a controls a servo-piston 16a which operates through a linkage 84, 83, 82, 81, 79, 80 arms 13, 14 connected to adjust the usual racks acting on the plungers of the fuel injection pumps. The above-mentioned linkage includes a floating lever 79 connected through a lever 77 and a slotted cam 75 with the power control shaft 63. The movement of the power control lever 8a thus gives an initial setting to the pump control arms 13, 14 and this is subsequently corrected in accordance with the pressure drop across the metering orifice. The movement of the servopiston 16a in the fuel' increasing direction is limited by a stop 32a adjustable by a cam 34a which may be set to a normal running position determined by a stop 71 or to a full power position determined by a stop 72. The constant flow unit 46 comprises a fixed orifice 50 in series with a variable orifice 51 adjustable by a conical valve 52. The pressure drop across the orifice 50 is applied to a diaphragm 55 which actuates a balanced pilot valve 54. The valve 54 controls a servo-piston 53 which in turn adjusts the valve 52 to maintain a constant pressure drop across and hence a constant flow through the fixed orifice 50. The cam 68 provides additional adjustment for the metering orifice 60, 65, for instance in the case of an aircraft engine for reducing the quantity of fuel supplied above the critical altitude. In this case the means for adjusting the cam 68 is also connected to a rod 89 for adjusting the fulcrum 87 of the lever 77 and so effecting a reduced setting by the lever 8a. In a modification, the flow to the pumps is maintained constant for a given position of the power lever which as in Fig. 1 adjusts a sleeve 60. The pressure drop across the metering orifice 60, 65 is maintained constant by a servo-operated by-pass valve. The pump control arms are operated directly by the power control lever and also through a fluid pressure servo-mechanism by the pressure drop across a fixed orifice in the return line from the pumps 1, 2.